This invention relates generally to liquid particle/droplet detecting systems, and more particularly to systems for detecting particles or droplets of liquids, e.g., oils, solvents, aqueous liquids, etc., in gas systems making use of at least one high pressure gas compressor or other device which may introduce fine particles of such liquid(s) into gas in the system.
As should be appreciated by those skilled in the art, in gas producing, transport and/or storage systems that make use of high pressure gas compressors, it is highly likely that there will be some oil leakage from the seals of such compressors, which leakage is typically in the form of minute particles or droplets introduced into the gas stream (sometimes referred to as “oil droplet breakthrough”). Since the existence of such particles will contaminate the gas product, it is a common practice to make use of separators, coalescers, adsorbent beds, and filters in gas systems downstream of the high pressure gas compressor (or any other device which may introduce fine oil particles into the gas). Such devices are designed to capture such oil particles and thereby prevent them from contaminating the final gas product.
The patented prior art includes various particle detecting devices that make use of light scattering techniques to detect the presence of particles in fluid streams. For example, in U.S. Pat. No. 5,864,399 (Girvin et al.) and U.S. Pat. No. 5,642,193 (Girvin et al.) there are disclosed particle detectors, each of which employs a laser disposed in a resonant cavity and an intra-cavity view volume. The resonant cavity is defined by two spaced apart mirrors, with the laser medium positioned between them, defining a light path. A pump source is optically coupled to drive the laser medium to produce coherent light having a first wavelength. The view volume is positioned in the light path, between the first mirror and the laser medium, to introduce particles into the resonant cavity so that light impinging there-upon produces scattered light. A detector is disposed to sense light scattered from the view volume and produces signals proportional to the light sensed. A displaying device, such as a pulse height analyzer, is in electrical communication to receive the signals produced by the detector to quantitatively display the intensity of the light sensed.
DE 10162278 discloses a system of detecting the presence of air compressor produced oil droplets in compressed gas stream by heating and expanding a partial aerosol stream, to thereby transform the droplets into a gas which is subsequently analyzed by a gas sensor.
Devices for detecting particles in a fluid stream are also commercially available. For example, Thermo Andersen, Inc., of Franklin, Mass. sells a HPM-1000 particulate monitor that is designed to be installed directly in line with compressed air/gas streams to provide continuous measurement of oil mist carryover, entrained water mist, and particulate contamination at pressures up to 350 psig. The HPM-1000 monitor uses a high sensitivity nephalometric (photometric) sensor, whose light scattering detection configuration has been optimized for the measurement of fine particle contamination in compressed air and gas streams.
While the aforementioned prior art is generally suitable for its intended purposes, it never the less leaves something to be desired from the standpoint of providing an on-line process monitoring system and method capable of detecting low levels of fine oil particles in a post compressor gas stream (or in a gas stream from any other device which may introduce fine oil particles into the stream) and, to alert an operator to a failure of the compressor seal before the oil is passed into the final product or to institute automatic remedial action, e.g., shut off at least a part of the system and/or bring another part of the system on-line to prevent the further contamination of the gas product.
The disclosure of the previously identified patents, patent applications and publications is hereby incorporated by reference.
The subject invention addresses those needs by providing systems and methods to aid in prevention of breakthrough of fine oil (or other liquid) particles into a downstream gas supply by monitoring the gas after the compressor at several points and reacting to any appreciable increase in oil levels. Moreover, the monitoring system is capable of detecting extremely low levels of oil particles. Thus, the usage of the systems and methods of this invention enables a more optimal usage of existing adsorbent beds and coalescers and does not require the transformation of the oil droplets into a gas.